Research Studentship: Coherent X-ray Imaging of Crystal Defects

3.5-year DPhil studentship

Project title: Coherent X-ray Imaging of Crystal Defects

Supervisor: Prof Felix Hofmann

Research Summary

We are seeking a DPhil student to join the Hofmann group at the Department of Engineering Science, University of Oxford, as part of the European Research Council funded project “AtoFun”.

Atomic scale defects, such as dislocations, play a central role in determining the physical and mechanical properties of crystalline materials. Transmission electron microscopy (TEM) revolutionised the study of dislocations by making it possible to see them. The interaction of dislocations with one another and with the surrounding microstructure is governed by the lattice strain fields every dislocation gives rise to. Probing these strain fields is a monumental challenge. For straight dislocations TEM measurements allow 2D imaging of strain fields perpendicular to the dislocation line. Unfortunately the vast majority of dislocation arrangements have more complex geometry and the study of strains due to tortuous dislocations remains beyond reach. Yet exactly these complex structures play the most important role in determining the behaviour of crystalline engineering materials.

Coherent synchrotron X-ray diffraction promises to provide a new approach for tackling this challenge. Recent measurements have shown that it allows the non-destructive 3D imaging of lattice strains in weakly strained nano-crystals. The challenge is to extend these types of measurements to highly strained samples, such as those containing dislocation structures.

The student will concentrate on developing new coherent X-ray diffraction approaches for probing specific dislocations. S/he will test these approaches on both semiconductor and metal systems and use them to study the strain fields associated with 3D dislocation structures. Furthermore s/he will use these new techniques to investigate the influence of impurities on dislocation strain fields. These exciting measurements will be combined with new simulations, developed by collaborators, that seek to predict the self-organisation of dislocation structures as well as the modification of dislocation strain fields.

The project will be carried out under the supervision of Prof. Felix Hofmann at the Department of Engineering Science, University of Oxford, UK. Other projects in the Hofmann group concentrate on the development of new TEM techniques for characterising atomic scale defects, as well as approaches for exploring the effect of defects on mechanical and physical material properties. There will be strong synergies between this DPhil project and these activities.

Prof. Hofmann’s research team is part of two “super groups”, consisting of 10+ academics each: the Solid Mechanics and Materials Engineering Group (SMMEG) in the Department of Engineering Science and the Materials for Fission and Fusion Power (MFFP) group in the Department of Materials. Weekly meetings of both provide an excellent platform for presentation of results and an active and stimulating environment for discussion with other researchers working in related fields. Further information about Prof. Hofmann’s research can be found at http://hofmanngroup.org and additional details about the Solid Mechanics Group in the Department of Engineering Science are available at http://www.eng.ox.ac.uk/solidmech.

Award Value

The value of the studentship is £22,000 per year. The student will be responsible for covering the cost of university and college fees (http://www.ox.ac.uk/students/fees-funding/fees).

Eligibility

This studentship is open to all applicants.

Candidate Requirements

Prospective candidates will be judged according to how well they meet the following criteria:

- Excellent degree in Engineering, Material Science, Physics, or another relevant discipline;
- Excellent analytical skills;
- Excellent written and spoken communication skills;
- Willingness to spend several weeks per year travelling to international collaborators and science facilities for experimental work (expenses will be covered).

The following skills are desirable:

- Ability to program in Matlab;
- Knowledge of optics;
- Knowledge of microscopy;
- Knowledge of material defect modelling.

Application Procedure

Informal enquiries are encouraged and should be addressed to Prof Felix Hofmann ([Email Address Removed]).

Candidates must submit a graduate application form and are expected to meet the graduate admissions criteria. Details are available on the course page of the University website.

Please quote 18ENGIN_09FH in all correspondence and in your graduate application.

Start date: October 2018